The title compound, C6H12O6, a C-3 position epimer of d-galactose, crystallized from an aqueous solution, was confirmed as β-d-pyran-ose with a (4) C 1 (C1) conformation. In the crystal, O-H⋯O hydrogen bonds between the hy-droxy groups at the C-1 and C-6 positions connect mol-ecules into a tape structure with an R 3 (3)(11) ring motif running along the a-axis direction. The tapes are connected by further O-H⋯O hydrogen bonds, forming a three-dimensional network.